1. Field of the Invention
The present invention relates to a device grinding process. More particularly, the present invention relates to a photoelectric device grinding process.
2. Description of the Related Art
In the present information age, electronic products have become indispensable part of our lives. We use electronic products in our work and in our home. In general, an integrated circuit device is at the core driving most electronic products. With the ever-advancing electronic technologies, more and more functionally powerful and personalized products are produced. Most of these electronic products can have a streamline, compact and miniature appearance largely due to a corresponding reduction in the size of semiconductor packages.
Due to the demand for small packages, the silicon wafer at the end of integrated circuit and device fabrication often has a thickness too large to fit into the package. Thus, before dicing up the silicon wafer, a tape is often attached to the active surface of the wafer and then the wafer is mounted to a polishing table to perform a grinding operation. After grinding the wafer to a thickness that meets the packaging requirement, the wafer is removed from the polishing table and the tape is removed from the wafer. Thereafter, another tape is attached to the back surface of the wafer before the wafer is cut into a plurality of independent chip units.
However, a delicate device such as the photoelectric device can be severely damaged if the aforesaid grinding process is deployed to reduce wafer thickness. In general, the photoelectric device has an image sensor or a micromechanical structure for fine tuning the radio frequency (RF) fabricated on the active surface of a silicon wafer using a semiconductor fabrication process or microelectromechanical technology. When a tape is used to mount the wafer on a polishing table, peeling the tape from the wafer surface at the end of the grinding process might cause severe damage to the micro-mechanical structures or the image sensors. Moreover, any tape residue left on the wafer after the tape peeling process might lower the yield of the photoelectric device. Furthermore, the photoelectric devices on the surface of the wafer need to be carefully protected during the grinding process. In addition, the mechanical strength of the silicon wafer will drop in accordance with the thickness of the wafer material removed in the grinding process. Hence, reducing the thickness of the wafer to a level suitable for packaging through a conventional grinding process is difficult.
Thus, there is a need for a method capable of grinding down the wafer to a suitable thickness without damaging the devices, especially, photoelectric devices or other micro-mechanical structures on the wafer surface.